The gamma-ray luminosity of spiral galaxies. Its evolution and its contribution to the diffuse background above 100 MeV

1978 ◽  
Vol 56 (2) ◽  
pp. 403-414 ◽  
Author(s):  
G. G. Lichti ◽  
G. F. Bignami ◽  
J. A. Paul
Keyword(s):  
Gamma Ray ◽  
Spiral Galaxies ◽  
Diffuse Background

scholarly journals Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

2018 ◽  
Vol 614 ◽  
pp. L1 ◽  
Author(s):  
A. Lähteenmäki ◽  
E. Järvelä ◽  
V. Ramakrishnan ◽  
M. Tornikoski ◽  
J. Tammi ◽  
...  
Keyword(s):  
Gamma Rays ◽  
Supernova Remnants ◽  
Gamma Ray ◽  
Spiral Galaxies ◽  
Narrow Line ◽  
Radio Jets ◽  
Relativistic Jet ◽  
Gamma Ray Emission

We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections.

Spectrum and origin of X- and gamma-ray diffuse background

1976 ◽  
Vol 209 ◽  
pp. 350 ◽  
Author(s):  
R. Rocchia ◽  
R. Ducros ◽  
B. Gaffet
Keyword(s):  
Gamma Ray ◽  
Diffuse Background

scholarly journals Soft gamma rays from low accreting supermassive black holes and connection to energetic neutrinos

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shigeo S. Kimura ◽  
Kohta Murase ◽  
Péter Mészáros
Keyword(s):  
Active Galactic Nuclei ◽  
Gamma Rays ◽  
Gamma Ray ◽  
Galactic Nuclei ◽  
High Energy ◽  
Hadronic Interactions ◽  
Neutrino Detectors ◽  
Accretion Flows ◽  
Diffuse Background ◽  
The Universe

AbstractThe Universe is filled with a diffuse background of MeV gamma-rays and PeV neutrinos, whose origins are unknown. Here, we propose a scenario that can account for both backgrounds simultaneously. Low-luminosity active galactic nuclei have hot accretion flows where thermal electrons naturally emit soft gamma rays via Comptonization of their synchrotron photons. Protons there can be accelerated via turbulence or reconnection, producing high-energy neutrinos via hadronic interactions. We demonstrate that our model can reproduce the gamma-ray and neutrino data. Combined with a contribution by hot coronae in luminous active galactic nuclei, these accretion flows can explain the keV – MeV photon and TeV – PeV neutrino backgrounds. This scenario can account for the MeV background without non-thermal electrons, suggesting a higher transition energy from the thermal to nonthermal Universe than expected. Our model is consistent with X-ray data of nearby objects, and testable by future MeV gamma-ray and high-energy neutrino detectors.

scholarly journals Constraints on the optical-IR extragalactic background from γ-ray absorption studies

2011 ◽  
Vol 7 (S284) ◽  
pp. 420-428 ◽  
Author(s):  
Luigi Costamante
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Background Light ◽  
Radiation Fields ◽  
Direct Measurements ◽  
Absorption Studies ◽  
Diffuse Background ◽  
Very High Energy ◽  
Tev Gamma Rays ◽  
Very High

AbstractVery high energy (VHE ≳0.1 TeV) gamma-rays from extragalactic sources, interacting by γ-γ collisions with diffuse intergalactic radiation fields, provide an alternative way to constrain the diffuse background light, completely independent of direct measurements. The limits depend however on our knowledge of the physics of the gamma-ray sources. After clarifying the interplay between background light and VHE spectra, I summarize the extent and validity of the obtainable limits, and where future improvements can be expected.

scholarly journals The effect of diffuse background on the spatially-resolved Schmidt relation in nearby spiral galaxies

2020 ◽  
Vol 634 ◽  
pp. A24 ◽  
Author(s):  
Nimisha Kumari ◽  
Mike J. Irwin ◽  
Bethan L. James
Keyword(s):  
Star Formation ◽  
Galaxy Formation ◽  
Spiral Galaxies ◽  
Formation Rate ◽  
Molecular Gas ◽  
Nearby Galaxy ◽  
Spatially Resolved ◽  
Diffuse Background ◽  
Nearby Galaxies ◽  
Atomic Gas

Context. The global Schmidt law of star formation provides a power-law relation between the surface densities of star-formation rate (SFR) and gas, and successfully explains plausible scenarios of galaxy formation and evolution. However, star formation being a multi-scale process, requires spatially-resolved analysis for a better understanding of the physics of star formation. Aims. It has been shown that the removal of a diffuse background from SFR tracers, such as Hα, far-ultraviolet (FUV), infrared, leads to an increase in the slope of the sub-galactic Schmidt relation. We reinvestigate the local Schmidt relations in nine nearby spiral galaxies taking into account the effect of inclusion and removal of diffuse background in SFR tracers as well as in the atomic gas. Methods. We used multiwavelength data obtained as part of the Spitzer Infrared Nearby Galaxies Survey, Key Insights on Nearby Galaxies: a Far-Infrared Survey with Herschel, The H I Nearby Galaxy Survey, and HERA CO-Line Extragalactic Survey. Making use of a novel split of the overall light distribution as a function of spatial scale, we subtracted the diffuse background in the SFR tracers as well as the atomic gas. Using aperture photometry, we study the Schmidt relations on background subtracted and unsubtracted data at physical scales varying between 0.5–2 kpc. Results. The fraction of diffuse background varies from galaxy to galaxy and accounts to ∼34% in Hα, ∼43% in FUV, ∼37% in 24 μm, and ∼75% in H I on average. We find that the inclusion of diffuse background in SFR tracers leads to a linear molecular gas Schmidt relation and a bimodal total gas Schmidt relation. However, the removal of diffuse background in SFR tracers leads to a super-linear molecular gas Schmidt relation. A further removal of the diffuse background from atomic gas results in a slope ∼1.4 ± 0.1, which agrees with dynamical models of star formation accounting for flaring effects in the outer regions of galaxies.

scholarly journals Forces attributed to dark matter may originate from entangled particles as seen in the shape of galaxies formed by GRBs

2018 ◽  
Vol 3 (5) ◽  
pp. 23-32
Author(s):  
Sándor Buglyó
Keyword(s):  
Dark Matter ◽  
Gamma Ray ◽  
Spiral Galaxies ◽  
Elliptical Galaxies ◽  
Spider Web ◽  
The Core ◽  
The Galaxy ◽  
Ring Galaxies ◽  
Barred Spiral Galaxies ◽  
Pass Through

Recently, it has been suggested that entangled particles may be connected by a wormhole. If that is right, what is the distance between them we have to take into account when applying Newton's law of universal gravitation to these particles? We propose the idea that these particles may attract each other regardless of distance, resulting in a force that behaves exactly the same way as the force derived from presumed dark matter. Traces of such a force seem to be present in galaxies due to gamma ray bursts (GRBs) that produce entangled particles which hit various objects. We can observe that in barred spiral galaxies the arms always pass through the nucleus of the galaxy so we believe that the very first GRB happened at the central supermassive black hole (SMBH) and the arms are the traces of this ancient GRB. If we see an unbarred spiral galaxy, we can be certain that the arms do not pass through the core and we think the very first GRB happened close to the core. Ring galaxies may also be considered as a type of spiral galaxies, since there is a section where the ring is broken, i.e. where the arms do not meet. So the very first GRB happened far from the core. Elliptical galaxies may have resulted from an ancient GRB which hit from outside. The arms rotating in opposite directions of the NGC4622 galaxy support our hypothesis. Finally in the silk threads of the spider web of the universe, the traces of GRBs can be seen.

scholarly journals Gamma Ray Pulsar Luminosities

2000 ◽  
Vol 177 ◽  
pp. 359-362
Author(s):  
Maura McLaughlin ◽  
James Cordes
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
Diffuse Flux ◽  
Upper Limits ◽  
Likelihood Analysis ◽  
Diffuse Background

AbstractWe apply a likelihood analysis to pulsar detections, pulsar upper limits, and diffuse background measurements from the OSSE and EGRET instruments to constrain theγ-rays pulsar luminosity law. We find a steeper dependence on period and magnetic field at OSSE than at EGRET energies. We also find that pulsars may be an important component of the OSSE diffuse flux, but are most likely not important for EGRET. We estimate that as many as half of the unidentified EGRET sources may beγ-rays pulsars. Furthermore, we predict that GLAST will detect roughly 1000γ-rays pulsars, only 100 of which are currently known.

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